On a foggy Wednesday morning atop the Gramercy Hotel in New York City, John Legend and Misty Copeland were practicing their dance moves.

"I got off a plane at 7 this morning and walked in here, and Misty was already dancing," John said. "It was like, 'okay, wake up John!'"

And while it's not unusual for the musician and ballerina to spend their days getting their groove on, the specific steps they were executing were a little out of the ordinary. It's what the folks at Wholesome Wave, a national food nonprofit, and Naked, a juice company, like to call the Shopping Cart dance — and it's part of their Drink Good Do Good social media campaign.

As part of a social media challenge, the dance is Wholesome Wave's and Naked's latest effort to raise funds and awareness for the 30 million Americans who either don't have access to fresh fruits and vegetables, or can't afford to buy them. "It's a fun way of educating people," Misty explained.

For every shopping cart dance video, Boomerang, or photo (which doesn't have to be done with a real shopping cart!) posted on Instagram, Twitter, or Facebook with the hashtag #FillYourCartForGood, Naked will donate the monetary equivalent of a shopping cart full of fruits and veggies, valued at $100, to Wholesome Wave.

Here's what you do:

1. Have a friend take a video, Boomerang, or photo of you doing the Shopping Cart dance with an imaginary shopping cart

2. Post your dance on Instagram, Twitter, or Facebook with the hashtag #FillYourCartForGood

The nonprofit provides affordable, quality produce to low-income families, and is relying on social media to help them do that this year.

"Sometimes people kind of make fun of social media activism... but I think it's powerful when you can use it as a platform to educate people, and move people in a direction where they're actually helping someone else," John said of the dance challenge.

Social-media activism becomes particularly effective when big names are attached: In addition to John and Misty's involvement in the Drink Good Do Good campaign this year, stars like Adrian Grenier and Kristen Bell have served as spokespeople in the past. Nora Quartaro, who oversees public relations at Naked, said the company tries to enlist celebrities who have grown up in food desserts (regions without access to quality produce), or "food celebrities." Misty admitted she grew up without means to good fruits and vegetables, while John is known to post cooking videos with his wife, Chrissy Teigen, on social media.

It also doesn't hurt that big names often have big followings. "We have millions of followers between us," John said. "Hopefully [we'll] get a lot of people involved so we can... feed a lot more people."

And as for John and Misty themselves? They plan on incorporating the Shopping Cart dance into their regular routines.

"She's going to do it on the Met stage. It's gonna be in my new Christmas video," John joked. "It's gonna be crazy!"

And in case you're curious what produce the two stars like to fill their carts with, Misty is into beets, carrots, and kale, while John flips over broccoli and spinach.